1. Field of the Invention
This invention relates to a magnetic recording medium, and more particularly, to a magnetic recording medium suitable for magnetic recording/reproduction systems for a high frequency recording with a further narrowed data-recording track width as well as advantageously available as a magnetic tape for recording computer data.
The invention also relates to a method for reproducing magnetic signals recorded in the above magnetic recording medium.
2. Description of Related Art
In recent years, along with popularization of mini computers, personal computers and office computers such as work stations, magnetic tapes for recording computer data as external recording media (so-called backup tapes) are used. It has been required for such backup tapes to have a large recording capacity and a high running durability along with the improvement of a computer information processing ability and the acceleration of processing speed. With spreading of the computer-using environments, the backup tapes are desired to have no occurrence of errors during recording and reproducing data, with high reliability, even under a variety of environmental conditions (especially, under the conditions with high fluctuations of temperature and humidity).
Various magnetic recording media have been developed with the aim at improving an output that corresponds to the shortest recording wavelength (xcex), especially to cope with high densification of magnetic recordings. For example, such a trial has been made as improving an analog SNR (Signal-to-Noise Ratio), thus to improve the SNR of signals by making a thickness of the magnetic layer 1.0 xcexcm or thinner, in a magnetic recording medium with a simultaneous multilayer structure which is a lamination of a nonmagnetic layer and a magnetic layer in this order on a flexible nonmagnetic support. With respect to digital signals, the SNR of the digital signals has been improved by improving an output at a high frequency equivalent to the shortest magnetization-reversing interval, thereby improving an error rate of the digital data with improving SNR of digital signals.
It has been tried that a laminated head is used as a reproducing head, mainly in a digital VTR for broadcast use or the like, for the purpose of improving an output and an SNR at the high frequency range. A laminated head here refers to a head with a structure forming magnetically superior sendust layers in the thickness direction of the conventional bulk ferrite head and accumulating magnetically separated layers (See, FIG. 1). The magnetically separated layers can be formed in the thickness direction by sandwiching the nonmagnetic layers, e.g., Si layers, in the thickness direction. A laminated head has a feature that an eddy current loss is hardly generated, especially in the high frequency range because each of the magnetic characteristics is separated between the thin layers in the thickness direction. This means that the laminated head has excellent characteristics in the high frequency range in comparison with a ferrite head.
Those challenges have been made to enhance an output in the high frequency area, make a good SNR with respect to digital signals and improve an error rate, by using such a laminated head exclusively as a reproducing head. However, SNR generated from using combination of a magnetic recording medium having the above-mentioned simultaneous multilayer structure and the laminated head is not enough to accomplish further high density recording such an improvement from DDS (Digital Data Storage)-3 to DDS-4 that specifications are shown in Table 1 as follows, and therefore further SNR improvement is required.
It is an object of the invention to provide a highly reliable magnetic recording medium allowing to provide further high density recording, serving advantageously as a magnetic tape for recording computer data, and having a further improved SNR.
It is another object of the invention to provide a method for reproducing signals magnetically recorded on a magnetic recording medium to make it possible to reproduce better magnetic recording such as computer data with high density recording.
The inventors have found out that, an excellent SNR and a low error rate that have not been obtained with conventional magnetic recording media are gained by reproducing magnetic signals, using a laminated head, recorded in a magnetic recording medium which comprises a magnetic layer and a nonmagnetic layer on a support, in which a thickness of the magnetic layer in a limited specific range.
The invention relates to a magnetic reproducing method which comprises detecting with a laminated head as a reproducing head, magnetic signals recorded on a magnetic recording media comprising a flexible nonmagnetic support having, in order, a nonmagnetic layer containing a nonmagnetic powder and a binder and a magnetic layer having a thickness in the range of from 0.2 to 0.6 xcexcm and containing a ferromagnetic powder and a binder.